The present invention relates to phthalazine derivatives, to the pharmaceutical compositions containing them and to their use as phosphodiesterase 4 inhibitors.
Phosphodiesterases are a family of isoenzymes which constitute the basis of the main mechanism of cAMP (cyclic adenosine-3xe2x80x2,5xe2x80x2-monophosphate) hydrolytic inactivation. cAMP has been shown to be the second messenger mediating the biologic response to many hormones, neurotransmitters and drugs [Krebs Endocrinology Proceedings of the 4th International Congress Excerpta Medica, 17-29, 1973]. When the suitable agonist binds to the cell surface, the adenylate cyclase activates and turns Mg2+-ATP into cAMP. cAMP modulates the activity of the majority, if not of all the cells contributing to the pathophysiology of various respiratory diseases, both of allergic origin and not. It follows that an increase of the cAMP concentration yields beneficial effects such as airway smooth muscle relaxation, inhibition of the mast cell mediator release (basophil granulose cells), suppression of the neutrophil and basophil degranulation, inhibition of the monocyte and macrophage activation. Thus, compounds able of activating adenylate cyclase or of inhibiting phosphodiesterases could suppress the undesired activation of the airway smooth muscle and of a great number of inflammatory cells.
In the phosphodiesterase family there is a distinct group of isoenzymes, phosphodiesterases 4 (hereinafter PDE 4), specific for the hydrolysis of cAMP in the airway smooth muscle and inflammatory cells (Torphy, xe2x80x9cPhosphodiesterase Isoenzymes: Potential Targets for Novel Anti-asthmatic Agentsxe2x80x9d in New Drugs for Asthma, Barnes, ed. IBC Technical Services Ltd, 1989). Studies carried out on this enzyme show that its inhibition yields not only the airway smooth muscle relaxation, but also the suppression of mastocyte, basophil and neutrophil degranulation, so as the inhibition of the monocyte and neutrophil activation. Thus PDE 4 inhibitors are effective in the therapy of asthma. Such compounds offer a unique approach to the therapy of various respiratory diseases both of allergic origin and not, and possess significant therapeutic advantages over the current therapy.
The excessive or irregular production of tumour necrosis factor (hereinafter TNFxcex1), a cytokine with proinflammatory activity produced by various kind of cells, affects the mediation or the exacerbation of many pathologies such as, for example, the adult respiratory distress syndrome (ARDS) and the chronic pulmonary inflammatory disease. Therefore, compounds able to control the negative effects of TNFxcex1, i.e. the inhibitors of this cytokine, are to be considered as useful against many pathologies.
The patent application EP 722 936 (Eisai) claims, inter alia, compounds of formula 
wherein n=0-4; R1 is optionally substituted lower alkoxy, optionally substituted cycloalkyl, or a xe2x80x94OR9 group wherein R9 represents an optionally substituted arylalkyl group; X is xe2x80x94Nxe2x95x90or xe2x80x94NR6xe2x80x94 wherein R6 is hydrogen, a lower alkyl group, or optionally substituted arylalkyl or heteroarylalkyl groups; Y is xe2x80x94CO or xe2x80x94CBxe2x95x90 wherein B is xe2x80x94NR7R8 wherein one of R7 and R8 may be H and the other an optionally substituted heteroarylalkyl group, or B is hydrogen or an optionally substituted aryl, heteroaryl, arylalkyl or heteroarylalkyl group; A is a hydrogen or halogen atom, or an optionally mono- or disubstituted amino group, an optionally substituted aryl, heteroaryl or heteroarylalkyl group. Among the groups optionally substituting the above mentioned residues, halogen atoms are cited. These compounds are said to be active as inhibitors of cGMP-PDE, i.e. PDE 5, a phosphodiesterase just acting through a cGMP-dependent mechanism and whose field of application is markedly cardiovascular (Schudt C. et al., Phosphodiesterase Inhibitors, Academic Press).
The patent application EP 634 404 (Rhone Poulenc Agriculture) describes, inter alia, phthalazinones of formula 
wherein R is an arylalkyl group, in particular pyridyl optionally substituted by halogen atoms; R1represents an alkyl chain up to 6 carbon atoms or an arylalkyl group, in particular phenyl; R2 represents a phenoxy or benzyloxy group; and m=0-4. These compounds are useful as pesticides.
The U.S. Pat. No. 3,274,185 (Messengill) describes, inter alia, phthalazines of formula 
wherein Y and Y1 are independently hydrogen or lower alkoxy; Z is phenyl optionally substituted by halogen or benzyl optionally substituted by lower alkyl or alkoxy; and R is hydrogen. These phthalazines are endowed with sedative and hypotensive activity, without mentioning the mechanism of action.
The U.S. Pat. No. 3,813,384 (Asta-Werke) illustrates, inter alia, benzylphtltalazinones of formula 
wherein R1 and R2 are hydrogen, lower alkoxy or halogen X is an optionally branched alkylene chain; m and n are 1-3; p is 0 or 1; and the group 
is an optionally substituted (C3-C8) mono, di- or tricyclic residue containing one or two nitrogen atom(s). Such compounds have hystaminolytic action and are useful, for example, in the treatment of asthma. All of the exemplified compounds show a residue 
which is a saturated heterocycle.
The patent application WO 97/40020 (Schering AG) describes compounds of formula 
wherein Y is xe2x80x94NR3xe2x80x94 or xe2x80x94Nxe2x95x90, R1 and R2 are H, lower alkyl, nitro, halogen, amino, lower alkoxy or xe2x80x94CF3, R3 is H, xe2x80x94COxe2x80x94 substituted by H, lower alkyl substituted by aryl, amino, lower alkoxy, cycloalkyl or cycloalkoxy, or R3 is lower alkyl or cycloalkyl, R4 is H or lower alkoxy, R5 is lower alkyl. These compounds are said to be uncompetitive antagonists of excitatory amino acids.
The patent application WO 97/48697 (Rhone Poulenc Rorer) describes bicyclic compounds with PDE 4 and TNFxcex1 inhibiting activity represented by a very broad general formula. Phthalazine compounds could be included in the general formula of this patent application, nevertheless none of the exemplified compounds is a phthalazine derivative and this kind of structure is excluded from the claims.
The patent application EP 848 000 (Tanabe Seiyaku) discloses, inter alia, phthalazine derivatives of formula 
wherein A is one of 
wherein R1 and R2 are H, or optionally protected hydroxy; R33 is lower alkyl; R5 and R6 are H, amino or may form a heterocycle. These compounds are PDE 4 inhibitors.
It has been now surprisingly found a new class of phthalazine derivatives able to inhibit PDE 4 and TNFxcex1.
Therefore the present invention relates to compounds of formula I 
wherein
 is a single or double bond,
Z is NH, methylene, a (C2-C6)alkylene chain optionally branched and/or unsaturated and/or interrupted by a (C5-C7)cycloalkyl residue;
A is phenyl or heterocycle optionally substituted by one or more substituent(s) selected among oxo, nitro, carboxy groups and halogen atoms, or a COR4 group wherein R4 is hydroxy, (C1-C6)alkoxy, amino optionally substituted by one or two (C1-C6)alkyl group(s) or by hydroxy;
R is a (C1-C6)alkyl or polyfluoro(C1-C6)alkyl group;
R1 is absent when  is a double bond or, when  is a single bond, is
a) hydrogen;
b) (C1-C6)alkyl optionally substituted by aryl, by heterocycle or by a COR5 group wherein R5 is hydroxy, (C1-C4)alkoxy or hydroxyamino;
c) xe2x80x94COR6 wherein R6 is hydrogen, aryl, aryl-(C1-C6)alkyl, amino optionally alkylated or monohydroxylated, hydroxy, (C1-C4)alkoxy, carboxy, (C1-C4)alkoxycarbonyl, 
or (C1-C4)alkyl optionally substituted by heterocycle;
d) (C1-C4)alkylsulfonyl;
R2 represents two hydrogen atoms or a group xe2x95x90O when  is a single bond, or, when  is a double bond, R2 is hydrogen, cyano, (C1-C4)alkoxycarbonyl, amido, optionally substituted aryl or heterocycle, (C1-C8)alkyl, (C2-C8)alkenyl or (C2-C8)alkynyl optionally branched and/or substituted by aryl or heterocycle; aryloxy, heterocyclyloxy, aryl-(C1-C4)-alkoxy, heterocyclyl-(C1-C4)alkoxy, amino substituted by one or two (C1-C4)alkyl group(s), arylamino, heterocyclylamino, aryl-(C1-C4)alkylamino, heterocyclyl-(C4)alkylamino;
R3 is hydrogen, or a (C1-C8)alkyl, (C2-C8)alkenyl or (C2-C8)alkynyl group optionally substituted by hydroxy, oxo, aryl or heterocycle, and optionally interrupted by one or more heteroatom(s) or heterogroup(s);
the Nxe2x86x92O derivatives of the compounds of formula I and the pharmaceutically acceptable salts thereof.
Preferred compounds according to the present invention are the compounds of formula I wherein  is a double or single bond; and Z is methylene or a (C2-C6)alkylene chain.
Still more preferred compounds according to the invention are the compounds of formula I
wherein  is a double or single bond; Z is methylene or a (C2-C6)alkylene chain; and A is a heterocycle optionally substituted by one or more substituent(s).
Still more preferred compounds according to the invention are the compounds of formula I
wherein  is a double or single bond; Z is methylene; and A is pyridine substituted by two substituents.
Within this class a preferred subset is represented by the compounds of formula I-A 
(formula I-Z is methylene, A is 3,5-dichloro-pyridin4-yl).
Still more preferred compounds are the compounds of formula I-A wherein  is a single bond and R2 represents two hydrogen atoms.
Another class of still more preferred compounds are the compounds of formula I-A wherein  is a double bond; and R2 is cyano, (C1-C4)alkoxycarbonyl, amido, optionally substituted heterocycle, (C2-C8)alkenyl or (C2-C8)alkynyl optionally substituted by aryl or heterocycle; aryloxy, heterocyclyloxy, arylamino, heterocyclylamino.
Within this class particularly preferred compounds are the compounds of formula I-B 
(formula I-A  is a double bond, R3 is hydrogen, R is methyl) wherein R2 is a heterocycle.
Specific examples of preferred compounds according to the invention are:
1-(3,5-dichloro-pyridin-4-ylmethyl)-6-methoxy-4-phenyl-phthalazine;
4-(3,5-dichloro-pyridin-4-ylmethyl)-7-methoxy-1H-phthalazin-2-carboxylic acid methyl ester;
benzyl-{3-[1-(3,5-dichloro-pyridin-4-ylmethyl)-6-methoxy-phthalazin-5-yl]-prop-2-ynyl}-methyl-amine;
1-(3,5-dichloro-pyridin-4-ylmethyl)-6-methoxy-5(5-morpholin-4-yl-pent-1-ynyl)-phthalazine dihydrochloride;
3-[1(3,5-dichloro-pyridin-4-ylmethyl)-6-methoxy-phthalazin-5-yl]-prop-2-yn-1-ol;
1-(3,5-dichloro-pyridin-4-ylmethyl)-6-methoxy-4-morpholin-4-yl-phthalazine;
1-(3,5-dichloro-pyridin-4-ylmethyl)-6-methoxy-4-[1,2,4]triazol-1-yl-phthalazine.
The compounds of formula I may have one or more asymmetric centre(s) and thus be in form of stereoisomers. Object of the present invention are compounds of formula I in form of stereoisomeric mixtures so as of single stereoisomers.
The compounds of formula I are active as PDE 4 and TNFxcex1 inhibitors and thus are used as therapeutic agents in allergic and inflammatory pathologies such as, for example, COPD, asthma and allergic rhinitis.
As heterocycle pyrrole, imidazole, pyrazole, pyridine, pyrazine, pyrimidine, pyridazine, piperazine, triazole, morpholine, pyrrolidine, pyrroline, imidazoline, pyrazoline, pyrazolidine, imidazolidine, piperidine, furan, pyran, thiazole, isothiazole, isoxazole, thiophene and the like are particularly meant.
Halogen atom means fluorine, chlorine, bromine or iodine atom.
Specific examples of alkyl groups are methyl, ethyl, n-propyl, i-propyl, n-butyl, s-butyl, tert-butyl, n-pentyl, 1-methyl-butyl, 2-methyl-butyl, 3-methyl-butyl, 3-methyl-2-butyl, n-hexyl, heptyl, octyl and the like. As (C5-C7)cycloalkyl group, cyclopentyl, cyclohexyl and cycloheptyl are meant, while aryl means an aromatic ring or system of 6-10 carbon atoms and specific examples of aryl and aryl (C1-C10)alkyl are phenyl, benzyl, phenethyl, phenyl-pentyl, naphthyl, indanyl, indanyl-pentyl and the like.
The oxidised form Nxe2x86x92O, if present, may involve both the nitrogen atoms present on the phthalazine ring and those present on A when it is a heterocyclic substituent. Pharmaceutically acceptable salts of the compounds of formula I are those with organic and inorganic acids, such as, for example, hydrochloric, hydrobromic, hydroiodic, nitric, sulfuric, phosphoric, acetic, benzoic, maleic, fumaric, succinic, tartaric, citric, aspartic, methanesulfonic, 3,7-di-tert-butylnaphthalen-1,5-disulfonic (dibudinic acid) or with inorganic bases such as, for example, sodium or potassium hydroxide, sodium bicarbonate.
The synthesis of the compounds of formula I proceeds according to methods known to the skilled in the art. For example, it can start from a compound of formula II 
wherein R and R3 are as defined above, and R2a is hydrogen, optionally substituted aryl or heterocycle or (C1-C8)alkyl, (C2-C8)alkenyl or (C2-C8)alkynyl optionally substituted by aryl or heterocycle, which can be prepared by different routes. For example, the treatment of a compound of formula III 
wherein R and R3 are as defined above, with a strong base, for example, n-butyl lithium, gives the compound of formula IIIa 
wherein R and R3 are as defined above and M is lithium or sodium, which treated with a formyl electrophile provides a compound of formula II wherein R2a is hydrogen. Such compound can be turned into a compound of formula II wherein R2. is other than hydrogen by treatment with a suitable organometal, for example, a Grignard reagent, to give a compound of formula IV 
wherein R, R2a and R3 are as defined above, which by oxidation, for example, with a pyridine-SO3 complex, DMSO and triethylamine, gives the desired compound II.
The compound of formula IV can also be obtained starting from a compound of formula IIIa by reaction with an aldehyde of formula V
R2axe2x80x94CHOxe2x80x83xe2x80x83(V)
wherein R2a is as defined above, used in molar excess as compared to the compound IIIa.
Also, a compound of formula II wherein R2a is other than hydrogen can be synthesised directly from a compound of formula IIIa by transmetallation with a suitable salt, for example zinc chloride, and subsequent reaction with an acyl chloride in the presence of a transition metal catalyst, for example, palladium.
After clearing of the oxazoline group of the compound of formula II, the treatment with hydrazine, in a protic solvent, is effected to give a phthalazinone of formula VI 
wherein R, R2a and R3 are as defined above, which treated with a halogenating agent such as, for example, phosphorous oxychloride gives a compound of formula VII 
wherein R, R2a and R3 are as defined above, and X is a bromine or chlorine atom. This, by treatment with a compound of formula VIII
Axe2x80x94Zxe2x80x94Yxe2x80x83xe2x80x83(VIII)
wherein A and Z are as defined above and Y is a metal such as, for example, Li, Na, Mg or a transition metal complex, gives a compound of formula I wherein R2 has the meanings listed above when  is a double bond and R1 is absent.
When a compound of formula I wherein R1 is present is desired, a compound of formula I wherein  is a double bond and R2 is hydrogen is treated according to methods known to the skilled in the art. For example, by reduction with hydrogen in the presence of Pd/C or PtO2, a compound of formula I wherein R1 is hydrogen is obtained, which by subsequent treatment with a suitable sulfonating or acylating agent, gives a compound of formula I wherein R1 is (C1-C4)alkylsulfonyl or xe2x80x94COxe2x80x94R6 wherein R6 is as defined above.
Alternatively, the compounds of formula I can be obtained starting from the acid of formula VIII 
wherein R and R3 are as defined above, which by reaction with formaldehyde and HCl gives a compound of formula IX 
wherein R and R3 are as defined above. This compound is halogenated, for example with N-bromosuccinimide in the presence of a catalyst such as benzoyl peroxide or 2,2xe2x80x2 azoisobutyronitrile, to give a compound of formula X 
wherein R, R3 and X are as defined above, which is treated with triphenylphosphine to give a compound of formula XI 
wherein R, R3 and X are as defined above, which is reacted with an aldehyde of formula XII
Axe2x80x94Zxe2x80x2xe2x80x94CHOxe2x80x83xe2x80x83(XII)
wherein A is as defined above and Zxe2x80x2 is methylene or a (C2-C5)alkylene chain optionally ranched and/or unsaturated and/or interrupted by a (C5-C7)cycloalkyl residue, or is absent, in the presence of an organic base such as, for example triethylamine, to give a compound of formula XIII 
wherein R, R3, Zxe2x80x2 and A are as defined above. This compound is reacted with hydrazine to give a compound of formula I wherein R1 is hydrogen, R2 is a group xe2x95x90O, and Z is methylene or a (C2-C5)alkylene chain optionally branched and/or unsaturated and/or interrupted by a (C5-C7)cycloalkyl residue, but not on the first carbon atom. The reaction of this compound of formula I with a suitable alkyl halide or sulfonate in the presence of a base, for example sodium hydride, gives a compound of formula I wherein R1 is a substituent other than hydrogen.
The compound of formula I wherein R1 is hydrogen can provide also other compounds of formula I wherein Z is methylene or a (C2-C5)alkylene chain optionally branched and/or unsaturated and/or interrupted by a (C5-C7)cycloalkyl residue, but not on the first carbon atom. For example, it is reacted with a halogenating agent such as, for example POCl3 or POBr3, to give an intermediate of formula XIV 
wherein A, R, R3, Z and X are as defined above, which is then subdued to a coupling reaction in the presence of a catalyst, such as for example palladium, or to an aromatic nucleophilic substitution, to give a compound of formula I wherein R2 has the meanings listed above when  is a double bond and Z is methylene or a (C2-C5)alkylene chain optionally branched and/or unsaturated and/or interrupted by a (C5-C7)cycloalkyl residue, but not on the first carbon atom.
As for the substituent R3 when other than hydrogen, it can be already present in the starting products of the various above synthetic routes or can be introduced and/or modified during the process according to methods known to the skilled in the art. For example, when R3 is (C2-C8)alkenyl or (C2-C8)alkynyl optionally substituted by aryl or heterocycle, it can be hydrogenated to give the corresponding (C1-C8)alkyl or (C2-C8)alkenyl residue. Said hydrogenation is effected according to methods known to the skilled in the art.
Alternatively, a compound of formula XV 
wherein R and R2 are as defined above, is activated on the hydroxy moiety, for example with triflic anhydride, to give a compound of formula XVI 
wherein R and R2 are as defined above, and W is an activating group. This compound is then subdued to a coupling reaction in the presence of a catalyst, for example palladium, to give the desired compound of formula VI which is then worked up as above described to give the compound of formula I.
The compound of formula XV can be obtained, for example, starting from a compound of formula XVII 
wherein R is as defined above and Bz is a benzyl group, which is oxidised, for example with potassium permanganate and tetrabutylammonium bromide, to give an acid of formula XVIII 
wherein R and Bz are as defined above, which by treatment, for example, with thionyl chloride, is turned into the corresponding acyl halide of formula XIX 
wherein R, Bz and X are as defined above. This is reacted with diethylamine in at least equimolar amount, to give a benzamide of formula XX 
wherein R and Bz are as defined above, which is reacted with dimethylformamide in the presence of a strong organic base such as, for example, butyl lithium, tert-butyl lithium, sec-butyl lithium, optionally in the presence of a ligand such as, for example tetramethylethylendiamine, to give a compound of formula XXIa 
wherein R and Bz are as defined above, and R2xe2x80x2 is hydrogen. This compound is reacted with hydrazine in acetic acid to give the compound of formula XXII 
wherein R, Bz and R2xe2x80x2 are as defined above, which is debenzylated with HCl in acetic acid to give the compound of formula XV.
The compound XXII, treated according to the methods already reported for analogous compounds (for example compound XVI) can also provide compound XXIII 
wherein R, R2xe2x80x2, W, Z and A are as defined above, which is reacted under coupling conditions with palladium to provide a compound of formula I wherein R2 is hydrogen.
An alternative for obtaining a compound of formula I wherein R2 is other than hydrogen foresees that the compound of formula XXIa is treated with R2xe2x80x3-magnesium halide, for example chloride, or R2xe2x80x3-lithium, wherein R2xe2x80x3 has the meanings of R2 above said but hydrogen, to give a compound of formula XXIV 
wherein R, Bz and R2xe2x80x3 are as defined above. The compound of formula XXIV is treated with a suitable oxidising agent such as, for example, pyridinium-chlorochromate and provides a compound of formula XXIb 
wherein R and R2xe2x80x3 are as defined above. The compounds of formula XXIa or XXIb are treated with acetic acid in acidic medium to give a compound of formula XXV 
wherein R and R2 are as defined above, which is reacted with hydrazine to give the phthalazinone of formula XV.
The synthesis of the N-oxide of the compounds of formula I is effected by treating the compounds of formula I with peracids such as, for example, m-chloroperbenzoic acid.
The preparation of the salts of the compounds of formula I is effected according to known methods.
The compounds of formula I are PDE 4 inhibitors as showed by the in vitro enzymatic inhibition activity tests (example 147), and also are able to inhibit the TNFxcex1 release (example 148). Comparisons with the following compounds were made: 6,7-dimethoxy-4-(pyridin-4-ylmethyl-2H-phthalazin-1-one (reference 1) and 6,7-dimethoxy-4-(piperidin-4-ylmethyl)-2H-phthalazin-1-one (reference 2) comprised by the general formula of the already cited patent application EP 722 936 (Eisai) and selected in view of the structural affinity with the compounds of the present invention. The reference compounds, though chemically similar, showed to be inactive as PDE 4 inhibitors.
Furthermore the compounds of the present invention did not show any activity on PDE 3 and 5 enzymes (example 149).
It is apparent how these selectivity and specificity features combined with the lack of activity on the cardiovascular system make the compounds of formula I specifically suitable for treating pathologies involving PDE 4 and TNFxcex1 such as asthma, the chronic obstructive pulmonary disease (COPD), the adult respiratory distress syndrome (ARDS), allergic rhinoconjunctivitis, psoriasis, atopic dermatitis, rheumatoid arthritis, septic shock, ulcerative cholitis, even if in the present contest the interest is particularly focused on the respiratory pathologies. Especially, the compounds of the invention are useful in the treatment of allergic and inflammatory diseases and above all in the therapy of COPD, asthma and allergic rhinitis.
The therapeutic doses shall be generally from 0.1 to 1,000 mg a day and from 1 to 200 mg by oral route for single administration.
A further object of the present invention are the pharmaceutical compositions containing a therapeutically effective amount of the compounds of formula I or pharmaceutically acceptable salts thereof in admixture with a suitable carrier.
The pharmaceutical compositions object of the invention may be liquid, suitable for the enteral or parenteral administration, and, preferably, solid such as tablets, capsules, granulates, suitable for the oral administration, or in a form suitable for the transdermal and inhalatory administration.
The preparation of the pharmaceutical compositions object of the invention can be effected according to common techniques.
For better illustrating the invention the following examples are provided.
The 1H-NMR spectra were run at 200 MHz on a Varian instrument; xcex4 are in parts per million.